carburetor flooding

[moosehorn02]

I have a 1968 dodge charger.I have owned it since 1981.The last 8years I have made lots of after market changes.It now has a 383 stoked to 496cui.I have had a problem with it flooding over after it has been driven and then sitting awhile.It stinks up the garage pretty bad.It does't matter what carburetor or how the floats are set.Is the fuel pump putting out so much pressure that it forces the gas through after it is shut off?How is that pressure normally released?I have a in line cartridge filter between the fuel pump and carburetor.It is a mechanical fuel pump.It is anew holley carburetor.Any help would be appreciated.
Mike

 

[bigmanjbmopar]

Do you have a fuel pressure gauge in line? If not get one should be 5-6 psi max with mechanical pump and the same with an electric pump. and it will drain back into the lines not the carb if you have your vent lines correct.

What are the details of the holley? cfm, model number? dual feed? double pumper?

When you stroked the motor what cam did you use? hydraulic cams need brass fuel pump rods for mech pumps.

Do you have a choke? electric or mech. are you sure it's set right? Are you sure your floats are set right? what size jets do you have? how is your timing set up? What are your Air/fuel mixerture screw set to?(how many turns in or out)

As you can see there are many possibility's, so start at one point and eliminate the simple causes first, there are a lot of guys here that will help you just make sure you provide as much info as possible.

 

[Meep-Meep]

Is the exhaust heat crossover open or blocked? If it's open this could be the problem because the new gas doesn't like to sit in a hot fuel bowl (at least in my part of CA that's the case). I had a similar issue with my old 352 Ford. I would shut it off after running it for a while and I'd smell gas. Even the breather hose would condense the gas vapors and fill up. Once I blocked the heat crossover the problem went away.

 

[moosehorn02]

Thank you for your response.I do not have a fuel pressure regulator and I do not have any return line to the gas tank.I did not think it needed that.Is there a return from the regulator or what?The holley is a Street avenger 0-80870. It has the two connections, one front ,one in back.The cam is a comp 21-242-4.The car starts, idles, and performs great,There is no run on or loading up or any thing.I do have an electric choke, and I have it set just about perfect for starting and opening fast enough, but not too fast to cause it to stall.I not not have a heat crossover since I have TTI headers.I think the idea about the fuel pressure and drain back is on the right track, but I am not sure what exactly I need to do in regards to the drain back/venting.I don not think there is any vent from the tank.I have had the tank out several times over the years, but can not remember any venting.If you can tell me what I need along those lines I can do it.Tanks again for your reply.

Scincerly Mike

 

[67 coronet]

you need to install a regulator and guage first.presher should end up at the 5 to 6 psi range as said before.you may want to check your gas tank as well.something needs to vent the presure back there as well.poss bad gas cap,or pluged vent line,depends on that design.

 

[oldbee]

Headers,cams,have nothing to do with it. The heat crossover is in the intake manifold,the ports are directly lined up sideways with the choke(hole) and carb.There were no return lines on normal 68's..Possibly on a/c cars,can't remember. You either have to use a thicker base carb gskt. to insulate carb from manifold or try setting float level a tad lower. Mopars always ran hot, but i never had a problem on my '68 Bee with either AVS or Holley on it.

 

[bigmanjbmopar]

Since you checked off a few things then I would go with either fuel venting or fuel boil, venting is fixed by having a non vented gas cap and the proper vent lines installed at the tank clear and working remember even with a full tank gas can slosh out the vents making it seem like gas is lingering around. Boil is fixed by a plastic spacer under the carb to absorb the heat and keep it from boiling in the bowl of the carb. Once you stop the heat from getting to your carb it should not smell of gas after you shut it off. heat in the engine is rising up and out and with today's gas like mentioned it does not take much for boil. Spacing the carb at least eliminates that possibility and is pretty in-expensive. you will never get the heat out of the engine bay but you can help dissipate it.

 

[moperformance]

next time you drive the car, open the gas cap to remove the pressure build up (if there is any) when you park it depending on the results you'll know which way to procede. Good Luck!

 

[green1]

All good tips. First, run it, turn it off, pull cleaner, flashlight in carb, and see if fuel is dribbling in. heat sink=1" plastic spacer (this will make it run better, with some more tuning).

Fuel pressure- buy a $8 gauge from harbor freight, and put it in line, and turn engine over 10 times, even start it. Most mech pumps are 7 psi. A $80 Carter will put out 100 gpm, but stay around 7 to 8.5. We just got through with this-a carter at 8.5 was not lifting the needle and seat on an addy 1407, holley 750.

Vents? while you have the breather off, look at the top of the carb, See at least 1 tube, about 1/4" id? that is the vent. Vent to tank is old emmisions crap, 40 years old, and has nothing to do with your problem. I bet heat soak (been there at least 10 times)

Retarded timing will heat up the engine, also.

 

[moosehorn02]

I appreciate all of the tips.I have already lowered the fuel level considerably with no change and I do already have the plastic spacer in place with a heat shield plate.I have figured out that it is not related to heat bcause I can drive the car for only 10 minutes in 20 degree weather , shut it off and later it will be real strong of raw gas.I have taken the air cleaner off when this happens and it is definetly stong smelling from the carburetor.I have not tried the fuel pressure regulator and gauge yet.I will try that and see what happens.Thanks again, any other ideas would be appreciated.

Mike

 

[bigmanjbmopar]

you sure your seal'd up at the fuel line to carb connection? unless you base gasket is broken or carb studs loose I don't know!? Cracked carb body? cracked manifold? leaking manifold gasket? Leaking fuel hose? broken fuel line strap?

If you have tried different carbs etc can only be some of the things above or over fuel preasure?

 

[FridayGt]

next time you drive the car, open the gas cap to remove the pressure build up (if there is any) when you park it depending on the results you'll know which way to procede. Good Luck!

Just had an issue like this myself. Previous owner had put in a new gas tank and not run any vent lines in it. He then placed a non-vented gas cap at the back. What was happening was that the vapors were building up pressure after parking it almost as though the pump was still pushing it. Vented the gas cap and presto. No more flooding carb.

To piggy back on moperformance's note, if you hear a hiss or any real kind of audible pressure release, it should let you know that that's your issue.